The most important thing about radiation

Traffic lights with red and amber lit up and a radioactivity sign on the amber.

Nuke Ampel, by NeilGHamilton on Flickr

Those of you who follow me on Twitter (@millysievert) will know that a few weeks ago I asked some questions about radiation and got more of a response than I had bargained for.

It started with “Hey, I’ve heard that cancer risk increases from a dose of 100milliSieverts, is that per year or some other duration?” It ended with me backing out of the days-long conversation entirely, taking some time away from Twitter and several weeks off blogging. The more information I was given the less I understood, and it was hard not to feel that this subject (and nuclear energy itself! I don’t do shades of grey very well) was simply beyond my comprehension.

A few weeks later I feel like I’ve finally, finally, figured out something useful: it’s not that this topic was beyond my comprehension; I was just asking the wrong questions, led by a misguided belief that the most important thing about radiation is the radiation itself when it very rarely is.

Yes, for professionals working with highly radioactive substances the radiation is indisputably the most important bit. But for a layperson like me – and we outnumber those professionals significantly – the most important thing about radiation is how acceptable a risk it presents to me. I asked questions about radiation to try and work out once and for all what risk it presents without considering just how intensely personal the concept of risk is.

I have never smoked. I don’t like feeling dependent on anything, increasing my everyday expenditure or standing outside in the cold. For me, any positives of smoking are not worth the increased risk of cancer. At the same time, I rarely wear sunscreen. I have skin that doesn’t burn easily, I hate the faff of reapplication every couple of hours and, as a Brit, I’m only occasionally in enough sunlight for long enough for it to be a consideration. For me, the positives of ignoring sunscreen are worth the increased risk of cancer.

Someone who has watched a loved one die from cancer might choose differently or be disgusted by my own choices. That’s valid. “Is this risky?” is a question not actually answered by a yes or a no; the answer depends on many variables, from past experience to family obligations to current standard of health to sheer gut instinct. Emotions are an important part of risk perception and should be respected as such. A decision made by one individual in one set of circumstances is no more or less rational than a decision made by another individual in different circumstances.

I am not suggesting that there is no point at which the risk of harm is objectively unacceptably high. There is a certain level of radiation to which nuclear professionals of every industry, education and amount of experience will agree humans should not be exposed, except in an emergency situation that would drastically distort the acceptability of risk. Below that level, however, there is not a consensus among nuclear professionals across the nuclear spectrum, which causes problems when trying to communicate the risk of radiation to laypeople – as I think the well-meaning professionals on my Twitter feed unintentionally demonstrated.

I was directed to link after study after book, and most recommendations were immediately refuted by other professionals with opposing opinions. Through this, the pattern I picked up on is a tendency towards one of two schools of thought on radiation exposure: do you believe permitted radiation exposure should be ALARP, As Low As Reasonably Practicable, or AHANE, As High As Naturally Existing? To put it a different way and take it to extremes, do you lean more towards thinking that radiation should be treated as automatically harmful unless definitely proven otherwise or automatically harmless unless definitely proven otherwise?

Both views make sense and come from the best of intentions. It is indisputable that radiation negatively affects the human body, and people have a right to know whether choosing a home or a job within reach of a nuclear power plant increases the possibility they may get cancer. However, it is important to be clear about how small that increase is and how that possibility compares to other activities – such as smoking, or choosing not to apply sunscreen.

There is a certain point below which most people will assess a risk to be insignificant. There are also points at which it is undeniably significant but we take the chance anyway, such as with driving a car, giving birth or taking a sedentary job in an office. These relatively high-risk activities add such great benefits to our lives (well, maybe not the office bit…) that we don’t let the scarily high numbers of illness, injury or death associated with them deter us from taking part.

Again, this is intensely personal. But that’s the point: there is no magic number at which radiation becomes safe for everyone, because the very concept of safety is, below a certain threshold of risk, flexible and individual and subject to many variables.  Would I personally expose myself to a higher level of radiation than the evacuation limit for Fukushima? Absolutely. What if I were pregnant? Suddenly the question is more complicated. Entrusted with my baby nephew? Now I have no idea.

Wanting to keep people’s exposure to radiation as low as possible is understandable, but does not necessarily weigh up the risk of exposure against other risk factors. People have died from the events of Fukushima. Not from the accident itself, but from psychological and physical stress from forced evacuations. How much does the possibility you may die from stress increase after you are evacuated from your home and not permitted to return? How about the possibility of suffering from depression, or of existing depression being exacerbated to suicidal levels? Of vulnerable hospital patients worsening or even dying sooner than was avoidable? Should such factors be taken into account when considering how much ‘risk’ is associated with maintaining an exclusion zone after a nuclear accident?

The most important thing I have learned about radiation is that we cannot always measure the risk of exposure by numbers alone. We need to promote a more nuanced understanding of risk than “Low-level radiation is harmless!” and “Low-level radiation is harmful!” This is part of a broader risk communication strategy we need to adopt industry-wide in which we acknowledge that emotions are important and integrate that understanding into our entire range of communications.

A final note: there is a chance that you object to any of my assumptions above. I know I’m on shaky ground, hence why none of my drafts from the past three weeks have made it up here. Just remember that I gained these impressions by asking questions of people who work with and study radiation, who gave me information and advice that I have been mulling over for weeks. If I’ve come out with the wrong idea about something, start considering how such professionals and experts can better collaborate on developing and distributing clear messages to give people like me when we start asking questions that we naively believe to be simple.


16 responses to “The most important thing about radiation

    • Thank you, that’s definitely useful to keep in mind! I think the problems of risk communication that I outline here exist in each of those categories, though I’ve no doubt they manifest in different ways depending on the category. Something I’ll need to think about more.


  1. Another thought-provoking read. Without wanting to muddy the waters I think it is worth noting some people will argue that there is a low level of exposure where radiation does not negatively affect the human body and there is a “magic number at which radiation becomes safe for everyone”. There are even those who argue for net positive effects at very low levels.

    But as you point out, not factored in is the emotional response. If people feel at risk from low levels of radiation that will likely have a negative impact on health more significant than the actual physiological effect, whether that actually is positive or negative. For that matter, if people believe (or believed) bathing in naturally radioactive hot springs would have a beneficial effect then it probably does some positive placebo effect.


    • Your second paragraph sums up exactly what I wanted to say with this post. The emotional and physical responses to stress are proven harmful or even fatal and must be taken seriously, but too often people in the nuclear industry don’t communicate this well. “Nobody died from Fukushima” is a common defensive response I’ve used myself in the past, but it lacks empathy and dismisses the other consequences exclusion zone residents have had to face. The human body is not the only part of a person that can sustain damage in an accident, and I think there is more we can do in this industry to publicly acknowledge and respect that.


  2. Great post again, Amelia! I like your personal style which gives your posts so much authenticity. Still I’d like to make one amendmend: You mentioned the “low-level radiation is harmful” and the “low-level radiation is harmless” schools. There is also a third school: “low-level radiation is beneficial”.


    • Thank you so much! Hormesis actually came up in the big Twitter conversation on this subject, but I decided to leave it to one side for now as too complicated and controversial to focus on just yet. I avoid topics like thorium and fusion for similar reasons – I’m struggling enough just trying to get my head around even the most evidence-based and supported facts about nuclear energy, I don’t have the confidence to explore ideas beyond that just yet!


  3. “…, but I decided to leave it to one side for now as too complicated and controversial to focus on just yet.” There seems to be the crux of the whole nuclear debate: Linear-No-Threshold vs Hormesis. In fact, the fallacies of LNT (IMHO) seems to have shaped the infrastructure of the nuclear industry more than E=MC²!

    Like you, I am a nuclear layperson. I became interested in sci-fi, and it’s basis in real science, at an early age. The last few years I’ve focused on nuclear energy/radiation and come to the conclusion that, while it is certainly controversial, it really isn’t all that complicated. In fact, I’m comfortable enough now with the idea of hormesis that I ordered a necklace from – which I wear about half the time.

    I’d encourage you (& your readers) to learn as much as possible about the LNT issues, which is not only at the root of safety regulations but drives many of the emotional responses of laypersons. As you have time, I’d encourage learning more from these resources.
    Prof Wade Allison’s book “Radiation and Reason”, and his online presentations.
    Gwyneth Cravens book, “Power to Save the World: The Truth About Nuclear Energy.”
    Galen Winsor’s testimonial at


    • Thank you for the links, I will definitely check those out! Great to meet another layperson too. 🙂

      I’m not sure it’s right to paint radiological protection views as hormesis vs. LNT; that seems like painting nuclear energy as fission vs. fusion or uranium vs. thorium. They are not mutually exclusive and they hold very, very different positions in the nuclear industry as it stands. LNT, for right or wrong, is used as the basis for all recommendations of safe dose limits while hormesis, for right or wrong, is dismissed as unfounded and even irresponsible by the people who make those widely-used and strongly supported recommendations. More than hormesis vs. LNT from what I’ve seen so far I would say that ALARP vs. AHANE is the biggest point of contention – and not likely to be resolved anytime soon.

      When I said hormesis was complicated I wasn’t necessarily referring to the difficulty of understanding the subject matter so much as the difficulty of approaching it in a way that radiological protection professionals could respect. There’s so much of interest in the sphere of nuclear energy, I’m trying to learn when to pick my challenges! 🙂 I don’t believe this was the right blog post to bring up hormesis, and I don’t regret not including it on this occasion.


  4. I had same difficulty understanding radiation units after reading Wade’s book asked questions of partner Geoff Sleeman he wrote Extinction The Climatic Time Bomb here’s result if it fits space:
    The original radiation units were named after the Curies and Radon (a gaseous form of uranium). These have now been dropped and replaced by units in the new international metric system (SI). There are different units for measuring radiation being emitted, the amount received, and the amount retained. They are named after the scientists who originally measured them.

    The Sun is an emitter of nuclear radiation. If you stand in the sunlight you will receive a small portion of this radiation which will tan or burn you. This is radiation received and if any of this radiation is left in your body or your skin this is radiation retained.

    1. The amount of radiation emitted by a source (such as Sun, nuclear energy units or X-ray) is measured in Becquerel’s (Bq). One Bq is 1 radioactive decay per second.

    2. The amount of radiation received by a source (such as the human body) is measured in Grays. One Gray (Gy) corresponds to one joule of energy absorbed by 1 kg of matter. A joule is a derived unit of energy in the International System of Units

    3. The biological (medical) effect of radiation is measured in Sieverts. The medically effective dose of 1 Sievert (Sv) corresponds to one Gy of x-rays.

    A source of confusion is the abbreviations used scientifically for small quantities of radiation. A one thousandth part of a Sievert is a milli Sievert denoted as mSv.

    A micro Sievert is a 1 millionth part of a Sievert and is denoted by the 12th Greek letter which is not available on most keyboards and so the prefix mu is used and is often confused (deliberately by oil, coal, or gas adherents ) with milli Sieverts whose prefix is m.

    Concerned scientific specialists consider that the UN radiation safety standards are set at 1000 times too low and this is due to false scientific reasoning. Now the chances of getting these safety standards promptly revaluated by the UN appear to be negligible.

    As nuclear radiation has its own energy it is readily detectable in very small amounts such as micro (1 millionth) Sieverts. As radiation is present in the soil, air and water it is also present to a small degree in most foodstuffs.

    A common radio isotope is potassium 40 (K 40). Potassium is essential to the human diet and a good source of potassium is bananas. For this reason the potassium content of bananas has been well studied and a unofficial radiation unit now in use is the Banana Equivalent Dose (BED). A BED is 0.0001 mSv (one millionth of a Sievert) and this amount is detectable by most radiation detectors.

    Airports with radiation detectors often have these set off by people carrying bananas.


    • Two small observations.

      Radiation spreads from a radioactive source. Somebody exposed to the radiation would be a receiver.

      0.0001 mSv would be 0.1 micro Sv.


      • Ken I’m travelling at present and I think it best to get Geoff Sleeman to expand on your questions when I see him again in a few days. This video of Prof. Wade Allison many find helpful. Japanese scientists asked him to do it: # : Also his book on Amazon/Kindle has the sigmoidal curve which helps understand advantage of radiation received. It’s rather like a big capital letter S fallen slightly to the right: then imagine an horizontal line thru about the middle of the S on a chart: Above the line the radiation becomes more dangerous as happens with anything that is overdone.

        I’ve seen 1 attempt at explaining this by top scientist whose workplace is funded by O&G industries & I was disturbed when he began his diagram right at bottom of chart where those really low levels we laypeople are trying to understand are and the horizontal line remained low too. This low level makes nuclear energy uncompetitive: Known as LNT Hypotheses. Big industries see to it that representatives sent to vote at UN on this level are from both Fossil fuel industries and their Unions.

        Air crews are exposed to more radiation than most. Careful documentation over many years show that compared with people of their own age from other walks of life, they live longer! This same careful documentation has been done in Japan as far back as Hiroshima/Nagasaki.

        I found it helpful to understand that yellowcake is centrifuged to 4 – 4 1/2% gas purity for health purposes, dentistry and reactors. The weapons grade procedure goes to 96% requires thousands of technicians and generators. That’s my layperson understanding so far.


    • “The Sun is an emitter of nuclear radiation. …”

      True. It also emits heat and light, but these should not be confused with the high energy ionizing radiation that reaches us in the form of cosmic rays. Heat and light are radiated with photon energy less than one thousandth of the energy of the weakest ionizing radiation. (Take a look at a chart showing the electromagnetic radiation spectrum.)

      Also, your short paragraph implies that the sun’s radiation can be retained in our bodies. That could only happen if we ingest radioactive material. The sun’s heat and light both reach us as electromagnetic radiation with no material involved,

      I’m being pedantic here. Once a teacher, always a teacher?


  5. Risk is a very hard thing to quantify, even with something as well studied as ionizing radiation. Adding a person’s emotional reaction to the calculation is indeed another important variable to add to the others (what type, dose, internal/external, genetic predispositions, etc). Sometimes a person may even have a positive outlook on radiation. My mother developed breast cancer in 1984. She had a mastectomy, however, the cancer had spread to her lymphatic system. The doctors gave her almost no chance for survival. She had witnessed the effects of chemo on both her parents and decided to go with just an aggressive radiation treatment. She’s still here today and has a pretty positive outlook on the effects of ionizing radiation. Something to consider, anyway.


  6. “Through this, the pattern I picked up on is a tendency towards one of two schools of thought on radiation exposure: do you believe permitted radiation exposure should be ALARP, As Low As Reasonably Practicable, or AHANE, As High As Naturally Existing? To put it a different way and take it to extremes, do you lean more towards thinking that radiation should be treated as automatically harmful unless definitely proven otherwise or automatically harmless unless definitely proven otherwise?”

    I think this is a brilliant analysis! You have pinned down the issues for normal people precisely!

    I am also a layperson in regards to Nuclear. I have been reading about it since 2008 and I experienced nearly the same path you have in regards to radiation. When I talk with Nuclear professionals I keep asking for comparative dangers. They are very reluctant to make direct comparisons preferring to fall back on the numbers in isolation from other common events. It makes a great deal of difference to my emotional outlook if I am accepting a “danger” or “hazard” that is about the level of walking down stairs, or running laps around a field. Or is the hazard from radiation closer to drinking acid? Closer to taking mega vitamins? What is comparable? As I have listened and read over the years I have found that regardless if the theory of LNT or Hormesis is accurate it makes nearly NO difference at the amounts of materials and radiation that are possible to release from a Nuclear Power plant. As I have teased out the actual effects, either the risks are so small they cannot be measured, or there is some small benefit. Either way, it is not a concern. I know we live in an age where mothers try to protect their children from everything. This is a change in societies toleration of risk and to our detriment in my opinion.

    Yes, let’s let people make choices, but let’s give them honest comparisons to make those choices with. People drive in the USA, even though we have all seen accidents. We rightly understand that 30,000 deaths a year is a fairly small number compared to the overall population. In any one year I have a 1 in 12,000 chance of dying in a auto accident. This is a very small number and a very acceptable risk.

    For potential radiation releases from Nuclear power plants what is the similar ratio? What is the chance of actually dying from the radiation we are exposed to in the most extreme accident? What is the chance of actually getting sick? Until we are given honest comparative numbers all the talk is just hand waving. I find that the ALARP, As Low As Reasonably Practicable people wave their hands a great deal and refuse to tell me straight what the risks are – as compared to other areas of life. Until that type of information is forthcoming the risks will always be assumed by lay people to be higher than they actually are.


  7. I would like to suggest going to the SARI site (Scientists for Accurate Radiation Information) The concept of relative risk is a necessary tool for defending the Linear/No Threshold assumption in the low level exposure region. What if LNT is wrong and use of relative risk rhetoric is not necessary? What if there is a real threshold of harm with respect to exposure? SARI addresses this and much, much more.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s